This invention relates to a boron cantilever and a method of making the same, particularly to a boron pipe cantilever for supporting a pickup stylus for converting shape signals recorded on a recording medium to electric signals, and a method of producing such cantilevers with a high production yield. According to this invention, a boron cantilever, particularly a boron pipe cantilever having a high mechanical strength and an excellent elastic ratio, E/.rho., can be obtained, where E is elastic modulus and .rho. is density.
Boron is known to have a hardness next to that of diamond and a very large resistance to abrasion, so that it is useful e.g. for cutting tools, sliding components and bearings. Further, since it has a low density and a large elastic modulus, the elastic ratio is largest among all the presently known materials. This means that the sound wave propagation velocity in boron material is highest among the presently known materials, so that boron is particularly useful for a cantilever for supporting a pickup.
It is difficult to obtain a dense body of boron by casting methods or rolling methods. So, usually, for making a boron cantilever, a boron coating is formed on a substrate other than boron by the vacuum deposition method, sputtering method or chemical vapor deposition (CVD) method, whereby the cantilever is composed of not only boron but also the substrate. This is disadvantageous, because the properties of the cantilever are deteriorated by the use of such substrate. It has been attempted to chemically or physically separate the boron layer from the substrate for obtaining a pure boron cantilever. However, there has been suggested no effective methods therefor. Further, according to the usual method, strain occurs between the boron layer and the substrate due to the thermal expansion difference between them, so that cracks are likely to occur in the boron layer, and thus it is difficult to obtain, in high production yield, a boron cantilever, having a high mechanical strength.
The present inventors have conceived of and attempted various methods for eliminating the above described disadvantages of the conventional methods and of the conventional boron cantilevers, namely for obtaining pure or substantially pure boron cantilevers, particularly pipe cantilevers, having a high mechanical strength and a large elastic ratio in a high production yield. Thereby, a novel boron cantilever and a novel method of making the same having been invented in accordance with this invention.